Let's avoid holding cp_rwsem write lock during f2fs_sync_node_pages()
in block_operations(), then cp_rwsem write lock's coverage in checkpoint
can be shrunk, then it expects there will be more opportunity that
foreground operator can grab cp_rwsem read lock.

Signed-off-by: Chao Yu <[email protected]>
---
 fs/f2fs/checkpoint.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
index f7cb4277de70..7596faa0be45 100644
--- a/fs/f2fs/checkpoint.c
+++ b/fs/f2fs/checkpoint.c
@@ -1190,6 +1190,8 @@ static int block_operations(struct f2fs_sb_info *sbi)
                .for_reclaim = 0,
        };
        int err = 0, cnt = 0;
+       bool sync_lockless = true;
+       unsigned int retry_cnt = 3;
 
        /*
         * Let's flush inline_data in dirty node pages.
@@ -1249,15 +1251,25 @@ static int block_operations(struct f2fs_sb_info *sbi)
 
        if (get_pages(sbi, F2FS_DIRTY_NODES)) {
                f2fs_up_write(&sbi->node_write);
+               if (!retry_cnt--)
+                       sync_lockless = false;
+               if (sync_lockless) {
+                       f2fs_up_write(&sbi->node_change);
+                       f2fs_unlock_all(sbi);
+               }
                atomic_inc(&sbi->wb_sync_req[NODE]);
                err = f2fs_sync_node_pages(sbi, &wbc, false, FS_CP_NODE_IO);
                atomic_dec(&sbi->wb_sync_req[NODE]);
                if (err) {
-                       f2fs_up_write(&sbi->node_change);
-                       f2fs_unlock_all(sbi);
+                       if (!sync_lockless) {
+                               f2fs_up_write(&sbi->node_change);
+                               f2fs_unlock_all(sbi);
+                       }
                        return err;
                }
                cond_resched();
+               if (sync_lockless)
+                       goto retry_flush_quotas;
                goto retry_flush_nodes;
        }
 
-- 
2.25.1



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